Recently, in a so-called power seat for driving the vehicle seat by motor, a position of a movable member of the vehicle seat is detected for controlling the driving of the motor. As one of such type device, the patent document 1 discloses a device in which the output voltage is watched at an output terminal of a reed switch provided between a plurality of resisters forming a series current circuit and a series of switches is fixed to an upper rail, a series of magnetic materials having a magnetic pitch which is same with the arrangement pitch of the reed switches is fixed to a lower rail, wherein the reed switch is turned ON in response to the approach of the magnetic materials and the switch position is judged by an output voltage from a branch circuit and a seat position can be detected by such detected position of the reed switch. By this structure, the detection of movable member of the power slide device from the reference point to the absolute position can be achieved without complicating the structure.
Further, according to the patent document 2, the document discloses a device in which a screwed bar is rotated by a driving force of a motor through worm and worm wheel mechanism to slide the upper rail and the movement amount is detected by a sensor provided at the tip end of the screwed bar. The sensor identifies the reed switch by magnets at both poles which rotate in synchronization with the rotation of the screwed bar thereby to turn ON/OFF of the indentified switch turn. The switch turns ON one time per one rotation of the screwed bar. The number of turning ON of the switch is accumulated by an ECU separately provided.
Further, according to the patent document 3, as a detecting means for detecting a position of a manually operated seat, the relative position from a memorized point is judged from the pulse count. Two Hall elements, one displaced from the other in a sliding direction and a magnet are used and a plurality of lock holes, each being provided on a slide lower rail, apart from one another having an equal distance. Two phase pulse edges generated from the Hall elements under the opposed position with the plurality of lock holes are used for judgment of position including the position in sliding direction. Counting base point can be clearly identified without any complicated setting by just setting the detection target hole desired to be the position of the base point in the sliding area to be in non-alignment condition with the two Hall elements.
Patent Document 1: Japanese Patent Application Publication No. 1995-164930A
Patent Document 2: Japanese Patent Application Publication No. 2004-352081A
Patent Document 3: Japanese Patent Application Publication No. 2004-12305A